The present invention relates generally to apparatus and methods for delaminating or peeling thin laminated sheets of material and, in particular, to a method of and apparatus for adjustably delaminating sheets of dry laminar imaging media having different peeling characteristics.
Prior systems are known for processing sheets of dry laminar imaging media by delaminating or peeling certain layers therefrom following the formation of images thereon. One such approach is described in commonly assigned U.S. Pat. No. 5,159,352, wherein images are formed on a thermographic type of dry laminar imaging media by the selective application of heat to discrete areas of the medium. In this regard, one sheet of the medium of the thermographic medium comprises a substrate or "keeper" layer or sheet, an overlying peel sheet or "throwaway" layer adhesively connected by an intermediate multicomponent image forming layer which may include pigment material and a binder therefor. In the laminar composite sheet structure the adhesive bond between the substrate sheet and the image forming layer is, in its initial unexposed state, greater than the bond strength between the peel sheet and the image forming layer. As a result of exposure to thermal energy applied by lasers, the bond between the exposed portions of the image forming layer and the peel sheet becomes stronger than the bond existing between the substrate and the image forming layer. Portions of the image forming layer which have been exposed can be separated from portions which have not been exposed by delaminating the peel sheet from the substrate; whereby complementary images are formed on the respective peel sheet and substrate. Peeling layers from a thin laminate such as described above is, however, an extremely delicate process because commercially objectionable image artifacts can be introduced into the final images if the adjacent exposed and unexposed portions are not peeled in the intended manner.
The sheet delamination apparatus of the invention can be employed for the processing of various types of dry laminar imaging media, including those which provide images by resorting to different imaging mechanisms than heat. Such media forms the complementary images thereon by the selective application of different sources of energy. In the field of graphics arts imaging, there is a need for one imaging medium designed for the production of a duplicate of an original (i.e., a right-reading positive image, referred to as a "dupe" image) and another imaging medium for the production of a right-reading negative image of the original (referred to as a "contact" image). It will be appreciated that laminar imaging media of "dupe" and "contact" types will be based upon different chemical formulation and will provide their respective images by the operation of different imaging mechanisms. Accordingly, the forces required for separating the respective layers will differ in a predetermined manner.
It is, therefore, highly desirable to be able to use the same apparatus for optimally peeling different imaging types of imaging media having respectively different peeling characteristics.